Device for preparing plastics material
A device for the preparation of plastics material, in particular thermoplastic plastics material, has a receiving container (1) for the material, the interior of the said receiving container (1) having tools (21) provided therein which are arranged on a carrier disc (9). The tools are driven by a shaft (4) for rotation about the, in particular vertical, axis (8) of the shaft (4). At least one screw (17) is provided for the removal of the material out of the receiving container (1). The screw housing (16) has a feed opening (27) which is connected with respect to flow to a discharge opening (15) in the container (1), which discharge opening (15) is situated at a lower level than the carrier disc (9) and the tools (21) carried by it. Further moved tools (12), which convey the material into the discharge opening (15), are provided in the receiving container (1) below the carrier disc (9). The carrier disc (9) comprises at least one aperture (36) which connects the space (26) above the carrier disc to the space (10) below it, in order to divert water vapour and/or gaseous substances out of the space (10). The apertures (36) are situated close to the axis (8) and close to the trailing edges (37) of the tools (21) during the rotation of the carrier disc (9).
Latest Erema Engineering Recycling Maschinen und Anlagen Gesellschaft m.b.H. Patents:
The invention relates to a device for the preparation of plastics material, in particular thermoplastic plastics material, with a receiving container for the material to be treated, the interior of the said receiving container having tools provided therein which are arranged on a carrier disc and which are driven by a shaft inserted into the interior for rotation about the, in particular vertical, axis of the shaft, and with at least one screw for removing the material out of the receiving container, the screw housing having a feed opening which is connected with respect to flow to a discharge opening in the receiving container, which discharge opening is situated at a lower level than the carrier disc and the tools carried by it, and further moved tools which convey the material into the discharge opening being provided in the receiving container below the carrier disc.
A device of this type, known from WO 00/74912 A1, has proved highly successful for the preparation of plastics material, in particular thermoplastic plastics material, but it has been found that a blocking-in of the volatile substances released by the treated material occasionally occurs in the space below the carrier disc. It is not always possible for these volatile substances to escape upwards through the annular gap existing between the edge of the carrier disc and the inner wall of the receiving container, particularly since the material, to be treated passes downwards from above through the said annular gap. It is particularly undesirable if the volatile substances are removed with the treated material out of the receiving container and arrive in the extruder which is attached directly or indirectly to the receiving container, since there is then a risk that inclusions of gas of various types will be present in the extruded material, and this substantially reduces the quality of the material contained at the outlet of thee extruder. This risk cannot be entirely eliminated even by a de-gassing device generally provided in the extruder. In addition, volatile substances of this type cannot generally be prevented from the beginning since they are water vapour, separation products of the material to be treated, gaseous or evaporated portions of coolant etc. In particular, in the case of moist plastics material introduced into the receiving container, these volatile substances can be substantial.
The object of the invention is to avoid these drawbacks and, with little outlay, to make the material removed through the discharge opening of the receiving container at least substantially free of the volatile substances mentioned above. This object is attained according to the invention in that the carrier disc comprises at least one aperture which is situated close to the axis and close to the trailing edges of the tools during the rotation of the carrier disc and which connects the space above it to the space below it. By means of the said aperture, the volatile substances present in the space below the carrier disc or at least formed there can escape upwards through the carrier disc into the space above it, where they are harmless and from where they can escape if necessary. In this case, it has been found from tests than apertures situated close to the axis are more effective than apertures situated at a distance from the axis. Such apertures situated at a distance from the axis are known from EP 625.373 A2 or DE 28 44 164 A, but are used there for the passage of crushed materials from the space above the disc to the space below it. In contrast thereto, the apertures according to the invention situated close to the trailing edges of the tools during the rotation of the carrier disc make use of the suction effect produced by the rotating tools in order to draw away the aforesaid volatile substances out of the space below the carrier disc.
In accordance with a further development of the invention, it is advantageous for at least one of the apertures to be constructed with walls which extend at an inclination to the direction of the axis and to the plane of the carrier disc. This tends to prevent material present in the space above the disc from dropping down through the carrier disc. A similar effect can be achieved within the scope of the invention by a cover which is provided for at least one of the apertures and which covers the aperture all round apart from an opening directed towards the periphery of the carrier disc.
The size of the apertures depends upon the quantity of the volatile substances to be removed. It has been found by tests that it sufficient for the cross-sectional area of all the apertures to be made at most as large as the cross-sectional, area of all the screws of an extruder connected with respect to flow to the discharge opening of the receiving container.
Further characterizing features and advantages of the invention may be seen in the description of embodiments of the subject of the invention, which are illustrated diagrammatically in the drawing.
In the case of the embodiment according to
Instead, the screw 17 can also be a conveyor screw only, which conveys the material prepared in the container 1 on for further use, for example to an extruder.
In operation, after a brief start-up time a state of equilibrium is formed between the material removed by the worm and the material entering the space 10 from above through the annular gap 11. This has the result that it is highly improbable that a particle of plastics material introduced into the container 1 will arrive in the screw housing 16 without having first spent an adequate residence time in the container 1. This ensures that all the particles of plastics material are acted upon to a sufficient extent by the tools 12, 21, so that the material removed by the screw 17 has an at least approximately uniform nature, in particular with respect to the temperature and the size of the particles of plastics material. This means that the plasticization action to be exerted by the screw 17 or the attached extruder screw is comparatively low, so that high thermal peak stresses upon the plastics material during the plasticization action are eliminated. As a result, the plastics material is spared and considerable savings are made in driving energy for the screw 17 or the extruder screw respectively.
As mentioned the material introduced into thee container 1 is not completely dry as a rule and/or it has impurities which, during the processing in the container, release volatile substances, for example water vapour, separation products from the treated material, evaporated coolant, volatile substances from inking and/or printing material etc. In order to prevent the said volatile substances from collecting in the space 10 below the carrier disc 9 and thus obstructing the passage of the treated material from the space 26 into the space 10 and/or penetrating into the interior of the screw housing 16, the carrier disc 9 has at least one aperture, and preferably a plurality of apertures 36, which connect the space 26 above the carrier disc 9 to the space 10 situated below it. As a result of the said apertures 36, the volatile substances blocked-in in the space 10 can escape upwards through the carrier disc 9 and thus pass out of the container 1 or can be removed, for example by a suction means 34 (
These apertures can be formed by bores of circular cross-section. At least some of the said apertures 36 are arranged close to the axis 8 of the container 1, namely immediately behind the tools 21, so that the apertures 36 are situated adjacent to the trailing edges 37 of the tools 21 as viewed in the direction of rotation (arrow 23) of the carrier disc-9. The suction effect produced by the tools 21 at their leading edges during their rotation assists the suction of the volatile substances upwards through the apertures 36. The axes of the apertures 36 can be arranged vertically, but it is more advantageous for the said axes 38 to be arranged obliquely (
In addition, it is advantageous to provide the apertures or at least some of them with a cover 28 (
The size, i.e. the cross-sectional area of the apertures 36, depends upon the quantity of the volatile substances to be removed. As a rule, it is sufficient for the cross-sectional area of all the apertures 36 to be dimensioned as large as possible, such as the cross-sectional area of all the screws of the extruder connected with respect to flow to the discharge opening 15 of the container 1, or of the screws 17 respectively.
The embodiment according to
It is advisable to monitor the temperature of the material treated in the container 1. To this end, as shown in
As already mentioned, the removal of the volatile substances entering the upper cutter space 26 can be assisted by a suction means. To this end, it is possible, as shown in
Claims
1. A device for the preparation of plastics material, in particular thermoplastic plastics material, with a receiving container (1) for the material to be treated, the interior of the said receiving container (1) having tools (21) provided therein which are arranged on a carrier disc (9) and which are driven by a shaft (4) inserted into the interior for rotation about the, in particular vertical, axis (8) of the shaft (4), and with at least one screw (17) for removing the material out of the receiving container (1), wherein the screw housing (16) has a feed opening (27) which is connected with respect to flow to a discharge opening (15) in the receiving container (1), which discharge opening (15) is situated at a lower level than the carrier disc (9) and the tools (21) carried by it, and wherein further moved tools (12) which convey the material into the discharge opening (15) are provided in the receiving container (1) below the carrier disc (9), characterized in that the carrier disc (9) comprises at least one aperture (36) which is situated close to the axis (8) and close to the trailing edges (37) of the tools (21) during the rotation of the carrier disc (9) and which connects the space (26) above the carrier disc (9) to the space (10) below it.
2. A device according to claim 1 characterized in that at least one of the apertures (36) has walls (40) which extend at an inclination to the direction of the axis (8) and to the plane of the carrier disc (9).
3. A device according to claim 1, characterized in that at least one of the apertures (36) has associated with it a cover (28) which covers the aperture (36) all round apart from an opening (35) directed towards the periphery (43) of the carrier disc (9).
4. A device according to claim 1, characterized in that the apertures (36) have a circular cross-section.
5. A device according to claim 1, characterized in that the cross-sectional area of all the apertures (36) is at most as large as the cross-sectional area of all the screws (17) of an extruder connected with respect to flow to the discharge opening (15).
6. A device according to one of claim 1; characterized in that the further moved tools (12) situated in the space (10) below the carrier disc (9) are suspended in a pivotable manner on the carrier disc (9) or on the shaft (4) and/or are mounted in a fixed manner on a further carrier disc (29) situated below the carrier disc (9).
7. A device according to claim 6, characterized in that the further tools (12) are constructed in the form of mixers only or, with cutters, as crushing tools.
8. A device according to one of claim 1, characterized in that a temperature-measuring device (30) and a cooling device (33), in particular a coolant-spraying means, are provided for the space (26) above the carrier disc (9).
9. A device according to one of claim 1, characterized in that a temperature-measuring device (31) and a cooling device, in particular a coolant-spraying means (32), are provided for the space (10) below the carrier disc. (9).
10. A device according to one of claim 1, characterized in that a suction device (34) for removing volatile substances is provided above the cone of material formed by the rotating tools (21) in the receiving container (1).
Type: Application
Filed: Feb 2, 2005
Publication Date: May 4, 2006
Patent Grant number: 7291001
Applicant: Erema Engineering Recycling Maschinen und Anlagen Gesellschaft m.b.H. (Freindorf)
Inventors: Helmut Bacher (St. Florian), Helmuth Schulz (Linz), Georg Wendelin (Linz), Klaus Feichtinger (Linz)
Application Number: 10/547,899
International Classification: B29B 7/00 (20060101);